The present invention relates to an exhaustion device of the kind which is intended for the removal by suction of exhaust gases and other environmentally harmful gases from a working area or location, or from the exhaust pipe of an automotive vehicle, and which comprises a suction line which is connected at one end thereof to a central suction means or to a suction fan and the other end of which is intended to be connected temporarily to the working location or to the exhaust pipe of an automotive vehicle, or some like location, for the purpose of removing therefrom by suction waste or exhaust gases generated in the working location or by the automotive vehicle.
Exhaustion devices of this kind are used in vehicle workshops, vehicle-inspection localities and vehicle-repair shops which are intended for other types of motor vehicle than cars, lorries (trucks) and buses, e.g. for such vehicles as tractors, forestry machines and agricultural machines. The exhaustion devices are operative to remove the exhaust gases generated when running tests on the engines of such vehicles and/or when bench-testing the engines in closed areas. Such exhaustion devices are also used in other kinds of workshops and also in laboratories, for the purpose of removing by suction environmentally harmful gases and vapours that are generated in such working locations, e.g. for the removal of welding gases from welding sites and from cutting machines. Exhaustion devices of this kind normally include a flexible suction hose which is provided at one end thereof with a connector or like device operative to connect the hose to the exhaust pipe of an automotive vehicle, or to a gas-collecting box or like device arranged over a workplace. In order to enable the hose carrying the connector to be connected, for instance, to the exhaust pipe of a vehicle, it is necessary for the hose to have a given length, and the greater the length of hose available, the greater the spatial working range of the exhaustion device. In those periods when the device is not being used to remove exhaust gases or other environmentally harmful gases or vapours, it is necessary for the hose to be stowed in some way or another, so that the hose will not be left hanging, with part of the hose lying on the floor, and therewith cause an obstacle to other work.
In order to overcome this drawback, it is known to wind the hose onto a reel fixed to the ceiling or a wall of the locality concerned, such as to enable a required length of hose to be uncoiled from the reel and the hose connected to the vehicle exhaust pipe. Such reels are normally provided with a spring device which is operative to recoil the hose automatically, i.e. with a powerful spring which when the hose is pulled from the reel is tensioned to an extent sufficient to rotate the reel automatically when the pulling force is removed, and thus re-wind the hose. In order to achieve automatic re-coiling of the hose after use in the case of an exhaustion device of such a kind, it is necessary, however, to use an extremely powerful spring with the subsequent drawback that an extremely large force must be applied to the hose in order to draw the hose from the reel, particularly when the hose is to be uncoiled to the extent of its full length. If the hose is not unwound to its full length, since a shorter hose-length will suffice, as is often the case, the flow resistance through the remaining turns of the hose will increase, resulting in a reduction in the exhausting ability of the device.
As a result of these and other drawbacks this kind of gas-exhausting device has been used to an increasingly smaller extent and the device has been replaced with exhaustion devices with which a required length of hose can be withdrawn from within a tube which is carried substantially horizontally by a wall-mounted, pivotal carrier arm and which is connected to a suction fan or to a central suction outlet located in a main suction line. The end of the hose located in the tube is sealed against the tube such that when the hose is release and the connector is closed and the suction-effect activated, the hose will be subjected to a subpressure which is operative to withdraw the length of hose extended from the tube to a predetermined position within the tube, in which position the hose length is withdrawn and will not therefore present an obstacle to other working activities. The subpressure required to withdraw the hose into the tube is achieved by providing the connector mounted on the hose with a cap or valve means operative to close the connector at the instance of disengaging the connector from an exhaust pipe, therewith enabling the subpressure required to retract the length of hose to be obtained.
The majority of known exhaustion devices are provided with such caps or valve means, primarily for the purpose of preventing air from being sucked from the locality concerned when the device is not in use, and therewith to prevent the occurrence of draughts and heat losses. Such caps are also operative to hold the hose connector in firm abutment with the outer surface of the vehicle-exhaust pipe, such as to ensure that the connector is not unintentionally disengaged from the exhaust pipe when removing exhaust gases therefrom by suction.
It is also known with this type of exhaustion device to use a wall-mounted or column-mounted winch, for the purpose of extending the substantially horizontally carried suction hose from its tube and for retracting the hose into the tube subsequent to use. In this case, the winch line is attached to the inner end of the suction hose and must therefore extend through the tube surrounding said hose, causing troublesome sealing problems as a result thereof. Consequently, with this type of exhaustion device, there is a serious risk that air will be sucked from the locality concerned, even when the device is not in use.
All of these known exhaustion devices equipped with retractable suction hoses which are partially carried substantially horizontally have the disadvantage of requiring the presence of a wall or support column in order to be mounted in the locality concerned, and consequently it is not possible to connect this type of exhaustion device to a ceiling-suspended main suction line which is located at a position remote from both walls and support columns. It is true that suction devices provided with ceiling mountable hose-reels can be used, although this solution is very expensive in comparison with the use of a suction hose which hangs directly from the main suction line and which is a very simple and inexpensive alternative from the aspect of cost, and although problems are experienced with regard to retracting the hose when not in use. This problem can be overcome with the aid of a ceiling-mounted balancing block of the kind described, for instance, in Swedish Published Specification 7709129-6 (publication No. 417162) or with a hose winch which is operative to coil the hose so that the hose will not constitute an obstruction when not in use. In the case of suction-hose suspension arrangements of this kind, the suction hose will present a bend, even when connected to a vehicle-exhaust pipe, resulting in increased flow resistance, and consequently such suction-hose suspension-devices have not been used to any great extent in practice.